We are investigating the safety of cardiopulmonary bypass in non-human primates which have received the investigational drug ANCROD. The Cardiology Branch has given this drug to patients with recurrent and persistent angina pectoris who are not candidates for surgery. No study to date has shown that these patients can safely undergo cardiopulmonary bypass without severe hemorrhagic complications. A strategy for reversing the defibrinogenating effects of ANCROD has been developed with the Hematology Section.